In general, a resin composition including polypropylene as a base resin has been widely used for various engineered plastic applications.
In order to reinforce physical properties of the polypropylene resin composition, a fiber reinforced composite has been prepared by mixing reinforcing fiber and the like with the resin composition and the composite has been used in the related art. Since such a resin composite of fiber reinforced polypropylene has improved physical properties, such as rigidity and heat resistance, compared to typical engineered plastics, the resin composite has been used as a functional engineered plastic widely in various industrial fields, in particular, in the automobile field, the electricity industrial field, and the like. However, problems still remain in other physical properties, and therefore, improvements have been continuously made.
In the related arts, a forming method and a forming apparatus of long-fiber reinforced thermoplastic resins has been introduced. For example, composite materials including glass fiber has been introduced.
Currently, the fiber reinforced polypropylene resin compositions may be one of the most widely used resins with enhanced rigidity or heat resistance by filling a polypropylene resin with reinforcing fiber, such as glass fiber or carbon fiber. From among these, in order to improve compatibility of a polypropylene resin with reinforcing fiber, required physical properties such as rigidity and heat resistance have been improved by adding a modified polyolefin which may be prepared by grafting maleic acid and the like with polypropylene to the polypropylene resin to increase compatibility with reinforcing fiber. As an example, a composition including an acid-modified polypropylene produced by adding polypropylene and maleic acid, and carbon fiber has been developed; and a resin composition including 100 parts by weight of polypropylene, 10 to 50 parts by weight of maleic acid-modified polypropylene, 5 to 65 parts by weight of carbon fiber, and 5 to 65 parts by weight of electroconductive carbon black has been reported. Further, a resin composition including 100 parts by weight of polypropylene, 0.5 to 20 parts by weight of a maleic anhydride modified polypropylene resin, carbon fiber or carbon black, glass fiber, and an inorganic filler has been suggested. Although above-mentioned polypropylene compositions may have excellent rigidity and thermal resistance, they may not be used for parts which have to withstand external impact due to their low tensile and flexural strength. Accordingly, aforementioned conventional polypropylene compositions may have poor impact energy absorbing ability, and break when they are used for vehicle molded products, for example, bumpers, external, and other internal parts.
Some attempts have been made to improve physical properties, for example, by adding rubber components or using a particular polypropylene. However, due to the particular polypropylene, improvement in tensile strength or impact absorbing ability, and the like may not be sufficient as compared to improved other physical properties such as rigidity, and accordingly, a problem of producing defective products has not been solved.
In other examples, a particular use of a propylene monomer having an isotactic index of 87 to 92 wt % (NMR reference standards) and a melt index of 0.5 to 35 g/10 min (230° C.) as a polypropylene base resin while a rubber elastomer is applied has been developed, but the composition also fails to solve a problem in that tensile strength or flexural strength, and the like are poor.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.